RECEIVing texts for digits

I agree this sucks and should be remedied. I spent a few weeks trying to figure this out myself and help from my local T-mobile store after purchasing a new phone. They were very helpful and knowledgeable. I highly recommend they as a store. But, this problem was a new one for them. In the end short codes are not available on my "digits" line (secondary line). Claimed as a security thing. The whole point of having access to short codes on my secondary phone is security so I can securely access my accounts. I can't even get payment updates from T-mobile saying my monthly payment went through. I can't get credit card purchase notifications. Just logging into this forum board right here for this post required me to switch phones just so I can read the short code.

If my secondary phone ("digits line") is registered to me and linked only to my number, authenticated, verified, in person with ID card in hand, and no other device can be linked to my number without me authenticating or approving it, then why can't this work? I don't really understand the security thing.